Sealed threaded joint for tubing pipes

ABSTRACT

The invention belongs to the oil and gas-extraction industry. The joint contains male ( 1 ) and female ( 2 ) elements with trapezoidal threads ( 3 ) with 1:16 taper and contacting each other taper sealing ( 5 ) and bearing ( 6 ) end surfaces. The slope angle between the thread profile lead-in flank ( 7 ) and the thread axis normal line amounts to 10-24°, the slope angle between the load flank ( 8 ) and the thread axis normal line amounts to −4 to +5°. The thread profile crests ( 9 ) and lead-in flanks make gaps ( 10, 11 ) in between, 0.05-0.15 mm wide, during joint make-up process. The thread profile on the area of mating of the load flank and the crest and on the area of mating of lead-in flank and the crest is produced rounded, with the different rounding radii for the male and female elements. The bearing end surfaces have a 10-20° slope angle with the thread axis normal line. A slope angle between the sealing surface of the male element and the thread axis normal line amounts to 13-18°, a slope angle between the sealing surface of the female element and the thread axis normal line amounts to 8-12°. On the female element on the thread run-out area and on the area of mating of the sealing and the bearing end surfaces are produced circumferential grooves ( 12 ) and ( 14 ). The female element area of mating of the sealing surface and the circumferential groove ( 14 ) surface and the male element area of mating of the sealing surface and the thread run-out surface are produced rounded. High tightness of the joint under sufficient mechanical loads, its wear resistance during multiple makes and breaks and its operation are achieved.

The given invention refers to sealed threaded joints for tubing pipes and can be applied for joining of the string elements, used at oil and gas wells exploitation, used for transportation of liquid and gaseous substances, as well as for overhaul and tripping operation.

The tubing of the oil and gas wells is exploited in complicated conditions, in corrosive medium and with huge mechanical load. Considering the abovementioned, the general requirement for the tubing pipes is high corrosion resistance, wear resistance, preservation of tightness at high loads, as well as high strength for provision of well passing ability, especially in areas with sufficient curvature.

At the state of the art there is a known sealed threaded joint for tubing pipes, which consists of the male and female elements, the ends of which, both externally and internally, are produced correspondingly with tapered trapezoidal threads, and contacting each other's tapered sealing and bearing end surfaces, which make internal sealing unit (RU 74661 UI, E21B 17/042, Oct. 7, 2008).

The given joint has the following shortcoming: low tightness of the joint at high combined mechanical load (tension, bending) application.

This engineering solution is made to provide the closest analog to the claimed invention.

The target to solve by the claimed invention—is to develop a sealed threaded joint for tubing pipes that can be applied for joining of the gas and oil well strings elements, operated at high loads.

The attainable technical result is the preservation of high tightness of the joint being affected by a sufficient mechanical combined load (tension and bending), preservation of wear resistance of the connection at multiple makes and brakes and at operation.

The specified technical result is achieved by presence of male and female elements of the sealed threaded joint for tubing pipes, the ends of which, both externally and internally, are produced correspondingly with tapered trapezoidal threads, and contacting each other's tapered sealing and bearing end surfaces, which make internal sealing unit. The bearing end surfaces make an acute angle with the corresponding sealing surfaces. The thread profile of the male and female elements at the area of mating of the load flank and the crest, as well as at the area of mating of the lead-in flank and the crest, is rounded. The profile crests and lead-in flanks of the male and female elements are made in such a way as to provide gaps in between at making-up of the joint. The female element of the joint has a circumferential groove (12) at the area of the thread runout, and a circumferential groove (14) at the area of mating of the sealing surface and the bearing end surface. The area of mating of the sealing surface and the circumferential groove (14) surface of the female element and the area where the sealing surface meets the area of the thread runout of the male element are produced rounded. A slope angle between the sealing surface of the male element and the thread axis line is 13-18°, and a slope angle of the sealing surface of the female element is 8-12°.

In particular, the bearing end surfaces of the internal sealing unit can have a slope angle with the thread axis normal line equal to 10-20°.

The radii of the roundings on the area of mating of the sealing surface and the circumferential groove (14) surface of the female element and the area where the sealing surface meets the area of the thread runout of the male element can reach 4-10 mm.

Circumferential groove (12) surface of the female element can be a direct extension of the female element sealing surface.

Circumferential groove (12) surface produces at making-up a hollow, which covers the first one and a half thread turns of the male element.

At an area where the load flank meets the thread profile crest and at an area, where the lead-in flank meets the thread profile crest, the radii of the thread profile roundings of the male element are bigger than the corresponding radii of the thread profile roundings of the female element.

The radius of the thread profile rounding on the area, where the load flank meets the thread profile, crest of the male element can come up to 0.2 mm, of the female element-to 0.1 mm; the radius of the thread profile rounding on the area, where the lead-in flank meets the thread profile crest of the male element can come up to 0.5 mm, of the female element-to 0.2 mm.

The slope angle between the thread profile lead-in flank of both female and male elements and thread axis normal line can come up to 10-24°, and a slope angle of the thread profile load flank can vary from or −4 to +5°, relative to the thread axis normal line.

Thread profile crests of both male and female elements can be produced in such a way as to form between them a gap of 0.05-0.15 mm wide at making-up of the joint.

Thread profile lead-in flanks of both male and female elements can be produced in such a way as to form between them a gap of 0.05-0.15 mm wide at making-up of the joint.

Trapezoidal threads of both male and female elements can be produced with 1:16 taper.

FIG. 1 depicts a made-up sealed threaded joint for tubing pipes.

FIG. 2 depicts the profile of the tapered trapezoidal thread, used for the sealed threaded joint for tubing pipes.

FIG. 3 depicts an internal sealing unit of the sealed threaded joint for tubing pipes.

The sealed threaded joint for tubing pipes consists of the male element (1), and the female element (2), the ends of which, both externally and internally, correspondingly, are produced with tapered trapezoidal threads (3) and contacting each other sealing (5) and bearing end (6) surfaces, which make internal sealing unit (4).

The male element (1) can be produced either in the form of a tube, pipe or a pin, while the female element (2)—in the form of a box or a coupling.

The thread profile (3) is made in a form of uneven-sided trapezium, the sides of which are the load (8) flank and the lead-in (7) flank. The above specified form of the thread profile lets the thread endure sufficient tension and provides the joint with easy make-up (prevents from jamming).

Thread profile (3) of male (1) and female (2) elements can be made with a slope angle between the lead-in (7) flank and thread axis normal line, equal to 10-24° and with a slope angle between the load (8) flank and thread axis normal line equal to −4 to +5°.

Thread axis normal line—is a perpendicular line to the thread axis line.

Producing a 10-24° slope angle between the lead-in (7) thread flank and the thread axis normal line provides stabilization of the male (1) element location relative to the female (2) element at the beginning of make-up procedure, which prevents from jamming of the joint and prevents the thread from damage (galling). Besides that, it provides a possibility for multiple makes and breaks of the joint and its high tightness.

Producing of a slope angle of the thread load (8) flank equal to −4 to +5° relative to the thread axis normal line prevents from cross-threading at sufficient tension (tightness loss), applied to the joint under the string run into the well self-weight.

When the joint is assembled (operational), the thread profile (3) crests (9) produced on the outer surface of the male (1) element and on the inner surface of the female (2) element, make a gap (10) between each other. Another gap (11) is produced by lead-in (7) flanks of the thread profile (3), produced on both male (1) and female (2) elements of the thread joint.

The gap (10) between the thread profile (3) crests (9) of the male (1) and female (2) elements provides for improved make-up of the joint and for its improved wear resistance, as well as it is used for letting out excess dope at making-up of the joint, accumulation of which on the contacting surfaces of the joint reduces its tightness.

A gap (11) between the lead-in (7) flanks of the thread profile (3) provides for the possibility of multiple makes and breaks of the thread joint without loss of its performance features (its high tightness, in particular) and its working efficiency. Besides that, a prevention from galling appearance in case of presence of foreign particles between the lead-in (7) flanks of the thread profile (3) on the male (1) and female (2) elements.

In particular, the width of the gap (10) between the tapered trapezoidal thread profile (3) crests (9) on the male (1) and female (2) elements can be 0.05-0.15 mm, and the width of the gap (11) between lead-in (7) flanks of the thread profile (3)-0.05-0.15 mm.

The thread profile (3) on the external surface of the male (1) element and on the internal surface of female (2) elements at the area of mating of the load (8) flank and the crest (9), as well as at the area of mating of lead-in (7) flank and the crest (9) is produced rounded.

And for both the area of mating of load (8) flank and thread profile crest (9) and for the area of mating of lead-in (7) flank and thread profile crest (9), the radii (Rb R2) of the abovementioned thread profile roundings on the male (1) element are bigger than the corresponding radii (R2, R) on the female (2) element—R>R2 H R3>R4.

In particular, the radius of the thread profile rounding at the area of mating of load (8) flank and the crest (9) on the male (1) element can come up to 0.2 mm; while on the female (2) element 0.1 mm. The radius of the thread profile rounding at the area of mating of lead-in (7) flank and the crest (9) on the male (1) element can come up to 0.5 mm; on the female (2) element-0.2 mm.

The rounding radius—is the radius of a circumference tangent to the load (8) flank and to the thread profile crest (9) or tangent to the lead-in (7) flank and to the thread profile crest (9).

Implementation of the rounding radius R1 at the area of mating of load (8) flank and thread profile crest (9) of the male (1) element bigger than that of R2 of the female (2) element provides a guaranteed contact on the straightline area of the thread profile (3) load (8) flank of the male (1) and female (2) elements at making-up of the connection for increasing of the thread elements resistance to wear off during the joint operation (wear resistance).

Implementation of the rounding radius R3 at the area of mating of lead-in (7) flank and thread profile crest (9) of the male (1) element bigger than that R4 of the female (2) element prevents the joint from jamming at the beginning of make-up and prevents the thread surface from damage (galling).

Trapezoidal threads (3) on the external surface of the male (1) element and on the internal surface of the female (2) element are produced tapered.

Performance of the threads (3) in a tapered form provides a high level of its tooth action in a made-up state and lets it to undertake high tension loads.

Trapezoidal threads (3) may have taper of 1:16.

Producing the threads (3) on the male (1) and female (2) elements with 1:16 taper provides the optimal taking by the joint of the bending and tensile loads, affecting during operation and during construction of the tubing string.

The internal sealing unit (4) of the joint is formed by contacting each other taper sealing (5) and bearing end (6) surfaces, produced on the ends of the male (1) element external surface and female (2) element internal surface.

At making-up of the joint, contacting each other taper sealing (5) and bearing end (6) surfaces due to elastic strain occurrence establish a thread or seal interference and “metal-to-metal” sealing and provide high tightness for the whole construction (joint) under complex loads and in severe service (in corrosive medium).

The bearing end (6) surfaces, produced on the male (1) element external surface and on the female (2) element internal surfaces, make an acute angle with the corresponding sealing (5) surfaces of the male (1) and female (2) elements.

The specified slope angle of the bearing end (6) surfaces provides additional “contraction” of the sealing unit, which permits to reduce the radial interference and consequently, reduces the possibility of the sealing (5) surfaces damage and galling occurrence on them. Besides that the contact area of bearing end (6) surfaces of the male (1) and female (2) elements increases due to its production on-the-mitre to the thread axis normal line, which permits to increase the make-up torque preserving contact stresses on a sufficient level within elastic strain.

In particular, bearing end (6) surfaces may be produced with a 10-20° slope angle to thread axis normal line.

In case the abovementioned slope angle between the bearing end (6) surface and the thread axis normal line exceeds the specified level, sufficient female (2) element inner diameter strains at compression or exceeds make-up of the joint start to occur. In case the slope angle is below the specified level—the “wedge effect” is lost as the female (2) element wedge becomes stiffer along the axis.

The sealing (5) surfaces of the internal sealing unit (4) of the joint, produced on the external surface of the male (1) element and on the internal surface of the female (2) element are not parallel to each other. The male (1) element sealing surface (5) slope angle to the thread axis line is bigger than that of the female (2) element.

The specified mutual location of the sealing surfaces (5) of the male (1) and female (2) elements provides high level contact stresses in the most distant from bearing end (6) surfaces area, which provides high tightness of the joint at combination of various limit loads.

The specified mutual location of the sealing surfaces (5) of the male (1) and female (2) elements provides as well its optimal contact area and a high level of contact stresses for the sealing surfaces (5) of the male (1) and female (2) elements, which consequently provides high tightness of the joint at all combinations of loads within all tolerance zones of the male (1) and female (2) elements.

The slope angle between the sealing surface (5) and the thread axial line of the male (1) element is 13-18°, of the female (2) element-8-12°.

The area of mating of the sealing surface (5) and the circumferential groove (14) of the female (2) element is produced rounded. The area of mating of the sealing surface (5) and the thread run-out surface (16) of the female (2) element is also produced rounded.

The specified roundings increase the contact area of the sealing surfaces (5) of the male (1) and female (2) elements, which has its influence over the joint tightness. Besides that, the specified roundings permit the joint to operate well at bending preserving high joint tightness at bending loads.

In particular, the rounding radii on the area of mating of the sealing surface (5) and circumferential groove (14) surface of the female (2) element (5) and on the area of mating of the sealing surface (5) and the thread run-out surface (16) of the female (2) element ¾ can come up to 4-10 mm.

On the joint female (2) element, on the area of the thread runout, there is a circumferential groove (12), that makes a hollow (13), covering the first one and a half thread turns on the male (1) element. The specified hollow (13) is limited (side view of the joint section) by the first one and a half thread turns on the male (1) element, the surface of the circumferential groove (12) on the female (2) element, the sealing surfaces (5) on the male (1) and female (2) elements and by the load (8) flanks of the thread profile on the male (1) and female (2) elements.

Producing of the specified circumferential groove (12), as specified above, excludes damages of the first imperfect thread (3) turn of the male (1) element at the beginning of the joint make-up with application of increase make-up torque. The hollow (13) made by the circumferential groove (12) serves for letting out the excess dope during the make-up process, which excludes the excess dope pressure on the joint and the tightness loss at yawn of the joint elements to each other as a result of excess dope.

The presence of the circumferential groove (12) on the female (2) element and on the made by it hollow (13) of the specified size permits to produce threading of the male (1) element without changing of the motion path of the cutting instrument at the end of the thread, which for granted, provides the accurate positioning of the male (1) element relative to the female (2) element due to accurate match of the bearing end (6) surfaces at the joint make-up.

The circumference groove (12) surface of the female (2) element is the direct extension of the sealing (5) surface of the female (2) element. The specified manufacture of the circumferential groove (12) surface and sealing (5) surface straightly, without angles and chamfering, provides for a smooth exit of the cutting instrument with no damage of the thread, which will further provide high joint tightness in a made-up state.

There is a circumferential groove (14) on the area of mating of sealing surface (5) and bearing end (6) surface on the female (2) element. The groove (14) makes a hollow (15), it is limited by (thread joint section side view) the bearing end (6) surfaces and the sealing surfaces (5) of the male (1) and female (2) elements, as well as by the groove (14) surface on the female (2) element.

The hollow (15), made by the said groove (14) is used for pushing out the dope excesses from the bearing end (6) surfaces at making-up of the joint. Besides that, a contact of male (1) and female (2) elements is excluded on the area of the groove (14) location. It prevents taper sealing (5) surfaces from pressing out at torqueing of the joint.

Location of the sealing (5) surfaces at a definite distance from the bearing end (6) surfaces prevents the internal sealing unit (4) from strains effect, that occur on the bearing end (6) surfaces at torqueing of the joint. The specified location of the contacting sealing surfaces (5) minimizes the surfaces (5) damage during production and operation of the joint.

The presence of the circumferential grooves (12) and (14) on the sealing surfaces (5) edges prevents the internal sealing unit (4) from the dope excesses effect, at it the dope excess is pushed out into the hollow (13) made by the groove (12) and by the male (1) element. The dope excesses from the bearing end (6) surfaces are pushed out into the hollow (15), made by the circumferential groove (14) and the male (1) element.

Sealed threaded joint for tubing pipes operates as follows.

The premier step at make-up process is to perform interaction of the male (1) and female (2) elements of the joint with the help of the tapered trapezoidal threads (3) produced on the ends on the external surface of the male (1) element and internal surface of the female (2) element.

During the make-up process forwarding of the sealing surface (5) of the male (1) element along the circumferential groove (12) of the female (2) element takes place. After that the sealing surface (5) of the male (1) element interacts with the sealing surface (5) of the female (2) element. Due to diametral strains of the tapered sealing surfaces (5) a “metal-to-metal” sealing is created.

The joint make-up process completion at movement of the male (1) and female (2) elements relative to each other goes with power contact of the bearing end (6) surfaces produced on the male (1) and female (2) elements which results in appearance of the contact stresses of the bearing end (6) surfaces, the values of which are within elastic strains range.

The bearing end (6) surfaces are produced in such a way, that when they are affected by the axial load occurring during the joint make-up, the transversal constituent of the specified axial load is directed to the joint axis. This excludes so-called “unrolling” effect—the transversal strain followed by the diameter increase in the area of bearing end (6) surfaces, which makes the joint less sensitive to exceeded make-up torque and increases the joint operational reliability.

Example of the invention realization.

Sealed threaded joint for tubing pipes consists of the male (1) and female (2) elements, on the corresponding internal and external surfaces, of which there produced tapered trapezoidal threads (3), and contacting each other taper sealing (5) and bearing end (6) surfaces, which make an internal sealing unit (4) of the joint.

The thread profile (3) of the internal and external surfaces of the male (1) and female (2) elements, correspondingly, is produced with the slope angle between the lead-in (7) flank and the thread axis normal line, equal to 18° and with the slope angle between the load (8) flank and the thread axis normal line, equal to 1° The thread taper is 1:16, pitch-4.233 mm.

The width of the gap (10) between the thread (3) profile crests (9) on the male (1) and the female (2) elements and of the gap (11) between the lead-in (7) flanks of the thread (3) profile amounts to 0.1 mm.

The radius of the thread (3) profile rounding at the area of mating of load (8) flank and the crest (9) on the male (1) element can come up to 0.2 mm; on the female (2) element 0.1 mm. The radius of the thread profile rounding at the area of mating of lead-in (7) flank and the crest (9) on the male (1) element can come up to 0.5 mm; on the female (2) element 0.2 mm.

The bearing end (6) surfaces produced on the external and internal surfaces of the male (1) and female (2) elements correspondingly, make an acute angle with the sealing surfaces (5) and are tilted to the thread axis normal line under 15° angle.

The slope angle between the sealing (5) surface and the thread axis line of the male (1) element amounts to 14°, and of the female (2) element-12°.

The female (2) element of the thread joint at the area of the thread runout contains a circumferential groove (12), which makes a hollow (13) and covers the first one and a half thread turns of the male (1) element.

The circumferential groove (12) surface of the female (2) element is the direct extension of the sealing surface (5) of the female (2) element.

The circumferential groove (14), making a hollow (15) is produced on the female (2) element, on the area of mating of the taper sealing surface (5) and bearing end (6) surface.

The soundings radii on the area of mating of female (2) element sealing surface (5) and circumferential groove (14) surface and on the area of mating of the male (1) element sealing surface (5) and the groove (12) surface amount to 5 mm.

The given thread joint provides the joint with increased tightness, with increased wear resistance of the joint during its multiple makes and breaks and during its operation, with endurance of sufficient tensile loads, as well as with the high level of ability of the joint inspection, which allows to use the given joint of the drilling string elements for both fluid and gas 

1. Sealed threaded joint for tubing pipes consisting of the male and female elements, on the external and internal surfaces of the ends of which are produced tapered trapezoidal threads and contacting each other the tapered sealing and bearing end surfaces, which make internal sealing unit, the bearing end surfaces make an acute angle with the sealing correspondence surfaces, this thread profile of the male and female elements at the area of mating of load flank and the crest as well as at the area of mating of the lead-in flank and the crest is produced rounded, the thread profile crests and the lead-in flanks of the male and female elements are produced in such a way to provide gaps in between at make-up of the joint, distinguished by circumferential groove (12) produced on the female element, at the area of the thread runout, and by the circumferential groove (14) produced on the female element, at the area of mating of the sealing surface and the bearing end surface, at this, the area of mating of the sealing surface and the circumferential groove (14) surface of the female element and the area where the sealing surface meets the area of the thread runout of the male element are produced rounded, the slope angle between the male element sealing surface and the thread axis line amounts to 13-18°, and the slope angle of the female element sealing surface-8-12°.
 2. The joint according to claim 1, distinguished by the bearing end surfaces of the internal sealing unit having an angle, equal to 10-20° with the thread axis normal line.
 3. The joint according to claim 1, distinguished by roundings radii at the area of mating of the sealing surface and the circumferential groove (14) surface of the female element and at the area where the sealing surface meets the area of the thread runout of the male element, come to 4-10 mm.
 4. The joint according to claim 1, distinguished by circumferential groove (12), at make-up process, makes a hollow that covers the first one and a half thread turns of the male element.
 5. The joint according to claim 1, distinguished by the female element circumferential groove (12) surface is the direct extension of the female element sealing surface.
 6. The joint according to claim 1, distinguished by the slope angle between the male and female elements thread profile lead-in flank and the thread axis normal line amounts to 10-24° and the slope angle between the thread profile load flank and the thread axis normal line amounts to −4 to +5°.
 7. The joint according to claim 1, distinguished by male and female elements thread profile crests are produced in such a way as to ensure making a gap of 0.05-0.15 mm wide between them during make-up process.
 8. The joint according to claim 1, distinguished by male and female elements thread lead-in flanks are produced in such a way as to ensure making a gap of 0.05-0.15 mm wide between them during make-up process.
 9. The joint according to claim 1, distinguished by the thread profile rounding radii of the male element on the area of mating of the load flank and the thread profile crest and on the area of mating of the lead-in flank and the thread profile crest are larger than the corresponding thread profile rounding radii of the female element.
 10. The joint according to claim 9, distinguished by the male element thread profile rounding radius on the area of mating of the load flank and the thread crest amounts to 0.2 mm, and the female element rounding radius amounts to-0.1 mm.
 11. The joint according to claim 9, distinguished by the male element thread profile rounding radius on the area of mating of the lead-in flank and the thread crest amounts to 0.5 mm, and the female element rounding radius amounts to-0.2 mm.
 12. The joint according to claim 1, distinguished by the male and female elements threads are produced with 1:16 taper. 